Lance with distance measuring sub-system

ABSTRACT

The invention is directed to an assembly which includes in combination a lance for supplying a gas to a nozzle in combination with radar-type means for determining the distance between the nozzle and a reflecting surface spaced from the nozzle. In the preferred embodiment, the assembly comprises an oxygen lance for a basic oxygen furnace which includes means for determining the distance between the lance and the surface of the charge in the furnace.

United States Patent 1 Bennett Apr. 17, 1973 LANCE WITH DISTANCEMEASURING FOREIGN PATENTS OR APPLICATIONS SUB'SYSTEM 1,434,231 2/1966France 266/34 LM l 75 Inventor: Robert George Bennett, Lowell,

Mass. Primary Examiner-T. H. Tubbesing [73] Assignee: Avco Corporation,Cincinnati, Ohio Anomey charles Hogan and Abraham Ogman [22] Filed: Feb.17, 1971 [57] ABSTRACT Appl. No.: 116,075

US. Cl. ..266/34 LM, 343/12 R Int. Cl. ..C2lc 7/00, G015 9/04 Field ofSearch ..343/l2 R; 266/34 LM References Cited UNITED STATES PATENTS10/1972 Herff ..266/34 LM The invention is directed to an assembly whichincludes in combination a lance for supplying a gas to a nozzle incombination with radar-type means for determining the distance betweenthe nozzle and a reflecting surface spaced from the nozzle. in thepreferred embodiment, the assembly comprises an oxygen lance for a basicoxygen furnace which includes means for determining the distance betweenthe lance and the surface of the charge in the furnace.

6 Claims, 3 Drawing Figures PATENTEDAPR1 1W 5.721897 SHEET 1 BF 2 PT/9'. 1. Y lzfl'w HMA'HYBRID INVENTOR 24 ROBERT G. BENNETT M- ATTORNEYSPATENTED APR 1 71975 SHLEI 2 UF 2 m a m 999 O Gwsfl 66M 99M 6 r SIGINALGENERATOR SIGNAL PROCESSOR Fig. 3.

INVENTOR ROBERT G. BENNETT ATTORNEYS LANCE WITH DISTANCE MEASURING SUB-SYSTEM There are a number of materials processes, typicallymetallurgical processes, wherein a gas is blown into a molten bathcomprising the materials charge, at high velocity from a lance. Thebasic oxygen steel making process is by far the most prominent example.

In virtually every lance application the position of the lance relativeto the charge bath is an important process variable. Position accuraciesof to 1 inch are sought. [t is also hypothesized that materialsprocessing may be improved if the lance position can be continuouslyadjusted during processes. At the present time, the lance position, orheight as it is called, is adjusted only at the beginning of a gas blow.

in the basic oxygen process, an oxygen lance supplies oxygen underpressure to one or more nozzles located at the tip of the lance. Thenozzles are located in a tip at the end of the lance located in thefurnace and spaced from the charge bath. Oxygen, during a blow, leaves anozzle opening as a supersonic effluent and impinges against the chargein the furnace. The distance between the nozzle and the charge, in thiscase the height of the nozzle opening, is a critical processingparameter.

The lance is 70 feet long. Heretofore, the spacing between the nozzleand the charge was determined at the top of the lance, 70 feet from thetip, by the location of a pointer in relation to a scale. This systemdoes not provide for variation in the length of the cable supporting thelance and variations in length in the lance due to temperaturedifferences.

Further, the pointer-scale system does not take into account theturbulence within the furnace, which turbulence causes variations in thedistance between the nozzle opening and the charge. The net result is anot too efficient system. A capability for measuring the distance of thenozzle opening from the charge continuously, to the nearest half inch toone inch is the design objective.

Heretofore, attempts have been made to measure the critical distance byattaching devices to the outside of the lance. Optical devices provedineffective because the charge surface is obscured by smoke and dirt,and molten particles. Radar-type measuring instruments mounted externalto the lance are also ineffective for the lack of stable reference withrespect to the nozzle opening.

It is an object of the invention to provide a lance system whichincorporates means for accurately measuring the distance between thelance tip, nozzle opening in the tip, and a charge surface.

Other objects of the invention are to provide in the foregoing describedlance system (I) radar-type distance measuring sub-system, (2) means forusing a nozzle as an antenna, (3) signal generating means located in theproximetry of the nozzle for reducing bandwidth requirements and foreliminating ambiguous readings, and (4) electromagnetic wave couplingmeans overlying the nozzle opening having means for providing anunimpeded flow of gas to the nozzle.

It is another object of the invention to provide a lance system with adistance measuring sub-assembly that avoids the limitations anddisadvantages of prior art systems in a relatively simple and reliablemanner.

It is another object of the invention to provide a lance system with anelectromagnetic wave distance measuring sub-assembly containing aperforated wave guide section for coupling the nozzle to a signalgenerator means without impeding gas flow.

In accordance with the measuring a lance assembly with anelectromagnetic wave sub-assembly for meansuring the spacing of thelance in relation to a reflecting surface comprises a gas carrying lanceterminating in a tip having at least one nozzle passage having anexterior opening. The lance assembly includes a transmitter and receiverlocated in the lance proximate to the nozzle passage. A coupling meansis provided for carrying signals to and from said nozzle passage fromthe transmitter and receiver. The nozzle passage and the nozzle openingact as an antenna. Signal generating and signal processing means arecoupled to the transmitter and receiver.

The novel features that are considered characteristic of the inventionare set forth in the appended claims; the invention itself, however,both as to its organization and method of operation, together withadditional objects and advantages thereof, will best be understood fromthe following description of a specific embodiment when read inconjunction with the accompanying drawings, in which:

HO. 1 is a partial cross-section of representation of the lance assemblyshowing the structural details of the transmitter-receiver, the coupling(transition) means, and the antenna-oxygen nozzle. The nozzle is alsoshown in a space relationship with respect to a reflecting surface.

H6. 2 is a schematic representation of a basic oxygen furnace with anoxygen lance in its operating position, and

HG. 3 is a perforated cylindrical member which forms part of theelectromagnetic wave coupling means.

Referring to FIG. 2 of the Drawings, there is shown a schematicrepresentation of a basic oxygen furnace 27 containing a charge 24 witha reflecting surface 26. A lance 28 is shown in its operational positionwithin the furnace 27. Typically, a lance is feet long. Oxygen iscoupled to the lance via pipe 29. Cooling water is inserted and removedthrough pipes 31 and 32.

A coaxial cable 18 is shown coupling the lance to the signal generator33 and signal processor 34 in a remote position from the lance. Aradiated signal from the nozzle of the lance to the reflecting surface26 is depicted at 36.

A signal generator 33 and signal processor 34 are coupled through acoaxial cable 18 to a transmitterreceiver 17 located within the lance(See FIG. 1). A component known as a hybrid acts as a transmitter andreceiver. lts process function will be explained hereinafter.

Refer to FIG. 1 of the Drawings. lt is a cross-sectional representationof the lower end of a typical basic oxygen lance 10. The lance isterminated in a tip 11 containing a plurality of nozzle 12 through whicha gas,in this case, oxygen, flows at supersonic speeds and impactsthrough a nozzle opening 23 on the charge 24.

Gas is supplied to the nozzles 12 by a pipe 16 which is coupled to theoxygen supply pipe 29 previously described in connection with FIG. 2.

A pair of concentric tubes 13 and 14 are coupled to pipes 31 and 32(FIG. 2) and are provided to supply and remove cooling water from thetip 1 l.

Continuing in connection with FIG. I, the hybrid 17 is coupled to theentrance 22 of one of the nozzles 12 by means of a transition section 19and a cylindrical section 21. The cylindrical section 21 is perforatedand more fully depicted in FIG. 3.

A second perforated section 25 is shown in combination with the otherleft nozzle 12. This is provided purely for aerodynamic reasons tobalance the forces caused by the flow of oxygen. The perforated cylinder25 forms a part of the electromagnetic distance measurin g sub-assembly.

The spacing of the hybrid 17 with reference to the nozzle opening 23 andthe distances to be measured from the nozzle opening 23 to thereflecting surface 26 are critical parameters. The distance separatingthe hybrid 17 and the nozzle opening 23 is designated D in FIG. 1 and 2.The smallest separation to be measured between the nozzle opening 23 andthe reflecting surface 26 is designated 1),. The symbol D represents thedistance between the smallest distance to be measured by the lancesystem and the longest distance to be measured. In short, it representsthe operating distance variation encountered by the lance.

The distance measuring sub assembly may be either a short pulsed or a CWsystem. With regard to the latter, it may be a linear FMCW system or asign wave FM-CW system. The foregoing systems are merely preferred forthe basic oxygen process but not exclusive. Other conventionalradar-type systems may be applicable in basic oxygen or othermetallurgical processes employing a lance.

For purposes of this discussion, a linear FM-CW system will bedescribed. The operation of the distance measuring sub-assembly is,briefly, as follows: A linear FM-CW signal is generated in the signalgenerator 33 and coupled to the hybrid 17 by way of a coaxial cable 18.The hybrid 17 couples the signal to the transitional section 19. Thesignal passes in sequence through the cylindrical section 21 and thenozzle 12. It becomes a radiated signal 36 (see FIG. 2) after it leavesthe nozzle opening 23. The radiated signal 36 impinges on the reflectingsurface 26 where a portion of the radiated signal is re-reflected backinto the nozzle opening 23, the nozzle 12, the cylindrical section 21and the transitional section 19 to the hybrid 17. The hybrid assembly 17may contain a crystal detector (not shown) which converts the signal toan audio signal. In this case, the audio signal leaves the hybrid viacable 18, and is coupled to the signal processor 34 where it isprocessed to provide a distance measurement.

The detector may be located at the signal processor if a favorablesignal-to-noise ratio can be maintained. Where the crystal detector islocated in the signal processor, the hybrid 17 functions as follows. Asmall portion of the transmitted signal is deliberately leaked into thereceiver section of hybrid I7 and is carried to the signal processor 34,as is a true received signal. The signal processor 34, moreappropriately the detector in the signal processor, operates on thetransmitted and received signal to generate the audio signalrepresenting the distance measured.

The signal processing is typically that of a linear FM system. Thetransmitted signal leaving the hybrid 17 causes a first reflection backthrough the receiver to the signal processor from the nozzle opening 23.The nozzle opening 23 represents a discontinuity that generates a smallreflection signal back to the signal processor 34. This first reflectedsignal from the nozzle opening 23 represents the reference from whichall distances are computed.

The signal returning from the reflecting surface 26, as is typical inall linear FM-CW systems, will generate within the hybrid an audiosignal having a frequency different from the audio signal reflected fromthe nozzle opening 23. The signal reflected may be synthesized in thesignal processor, since the distance from the hybrid to the nozzlesurface 23 is known and remains fixed. The signal processor computes thedistance between the nozzle opening 23 and the reflecting surface 26 onthe basis of, or the equivalence of, the difference in frequency betweenthe two reflected signals.

A number of combinations oflances and electromagnetic wave subassemblieswere tried and found to be unsatisfactory. For example, theelectromagnetic passage was mounted on the top of the lance and thetransmitted signal passed to the nozzle by using the center oxygen tubeor an additional tube as a wave guide. This was found to beunsatisfactory. A coaxial coupling between an exteriortransmitter-receiver and an antenna-oxygen lance proved equallyinoperative, as a practical matter.

In each case where the hybrid was mounted outside the lance, a number ofdistructive problems were noted.

Even when the hybrid 17 was located in the lance, difficulties wereencountered until it was determined that the distance from the hybrid 17to the nozzle opening 23 needed to be less than the shortest distance tobe measured, namely D,.

By using a modulation index for the FM-CW system of a least 200,interference from signals in the low audio frequency range such asamplifier l/f noise microphonics and 60 cycle power line interferencewas eliminated. An upper value of modulation index of 500 was selectedto keep the bandwidth requirements within economic and easily manageablerange. The modulation index represents the number of times thetransmitter sweeps through the FM frequency band per second.

While it is possible to construct a separate and distinct antenna withinthe lance oxygen pipe 16 an election was made to use an existing oxygennozzle 12 as the antenna. Accordingly, it was necessary to provide acoupling for both the electromagnetic wave signals and the passage ofoxygen from the center pipe 16 to the nozzle 12.

In this connection a perforated cylinder 21 coupling was designed andutilized in the manner shown in FIGS. 1 and 3. The perforations in thecylinder 21 should be smaller than 0.1 of the wavelength at theoperating frequency. The degree of containment of an electromagneticwave in a perforated cylinder can be estimated in accordance withprocedures described by W.W. Mumford in his article on Some TechnicalAspects of Microwave Radiation Hazzards" I.R.E.. Proceedings, Vol. 49,February 1961, pp. 445.

The complementary cylinder 25 associated with the second oxygen nozzlepassage shown in FIG. 1 is provided for dynamic stability and flowbalance and may be eliminated if the perforated cylinder 21 causes nomeasurable interference with the normal flow of oxygen.

The various features and advantages of the invention are thought to beclear from the foregoing description. Various other features andadvantages not specifically enumerated will undoubtedly occur to thoseversed in the art, as likewise will many variations and modifications ofthe preferred embodiment illustrated, all of which may be achievedwithout departing from the spirit and scope of the invention as definedby the following claims.

1 claim:

1. A lance assembly with an electromagnetic wave sub-assembly formeasuring the spacing of the lance in relation to a reflecting surfaceof a materials processing charge comprising:

a fluid carrying lance terminating in at least one nozzle having anozzle opening;

transmitter and receiver means located in the lance proximate saidnozzle opening;

coupling means for carrying signals to and from said nozzle from saidtransmitter and receiver, said nozzle and nozzle opening acting as anantenna; and

signal generating and signal processing means coupled to saidtransmitter and receiver.

2. A lance assembly as defined in claim 1 in which the distance fromsaid transmitter and receiver to the nozzle opening is D and thedistance from said nozzle opening to the reflecting surface is in therange of D, to D, D,, where D, is smaller than D,

3. A lance assembly as defined in claim 1 in which lance is an oxygenlance for a basic oxygen furnace, said transmitter and receiver arelocated in the oxygen supply pipe, and said antenna is an otherwiseconventional oxygen nozzle.

4. A lance assembly as defined in claim 3 in which said couplingoverlies the nozzle and includes means for providing unimpeded oxygenflow to said antennaoxygen nozzle.

5. A lance assembly as defined in claim 4 in which said couplingincludes a perforated cylinder interconnecting the oxygen supply pipeand said antenna-oxygen nozzle.

6. A lance as defined in claim 4 in which said transmitter modulationindex is 200-500.

i '0 I i Q UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3, 727,897 Dated April l7, 1973 Inventofls) Robert George Bennett Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, line L "measuring" Should read r invention,

lines 5 and 6, "meansuring" should {read measuring Signed and sealedthis 8th dayof January l97).

(SEAL) Attest:

EDWARD M.FLETCHE-R,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents FORM PC4050 (10-69) USCOMM'DC 60376-P69, 1 9 U.5. GOVERNMENT PRINTING OFFICE "l9 0-366-334. i

UNITED STATES PATENT OFFICE CERTHHCATE OF CORRECTFJN Patent No.3,727,897 Dated April ];7, 1973 Invmnmr s Robert George Bennett It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, line A, "measuring" should read invention,

lines 5 and 6, "meansuring" shouldread measuring Signed and sealed this8th day of January 197A.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYEE Acting Commissioner of PatentsAttesting Officer USCOMM-DC GONG-P69 w u.s. Govzmmzm' PRINTING OFFICE1909 o-ass-au,

FORM PC4050 (10-69) UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 727,897 Dated April 1?, 1973 lnventofls) RobertGeorge Bennett It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 2, line LL, "measuring" should read invention,

lines 5 and 6, "meansuring" should read measuring Signed and sealed this8th day of January 19714..

(SEAL) Attest:

EDWARD M.ELETCHER,JR. RENE D. TEGTMEYER Acting Commissioner of PatentsAttesting Officer

1. A lance assembly with an electromagnetic wave sub-assembly formeasuring the spacing of the lance in relation to a reflecting surfaceof a materials processing charge comprising: a fluid carrying lanceterminating in at least one nozzle having a nozzle opening; transmitterand receiver means located in the lance proximate said nozzle opening;coupling means for carrying signals to and from said nozzle from saidtransmitter and receiver, said nozzle and nozzle opening acting as anantenna; and signal generating and signal processing means coupled tosaid transmitter and receiver.
 2. A lance assembly as defined in claim 1in which the distance from said transmitter and receiver to the nozzleopening is D1 and the distance from said nozzle opening to thereflecting surface is in the range of D2 to D2 + D3, where D1 is smallerthan D2.
 3. A lance assembly as defined in claim 1 in which lance is anoxygen lance for a basic oxygen furnace, said transmitter and receiverare located in the oxygen supply pipe, and said antenna is an otherwiseconventional oxygen nozzle.
 4. A lance assembly as defined in claim 3 inwhich said coupling overlies the nozzle and includes means for providingunimpeded oxygen flow to said antenna-oxygen nozzle.
 5. A lance assemblyas defined in claim 4 in which said coupling includes a perforatedcylinder interconnecting the oxygen supply pipe and said antenna-oxygennozzle.
 6. A lance as defined in claim 4 in which said transmittermodulation index is 200-500.